The G0 Detector Status Report
Outline

Ken McFarlane has proposed that we have a working document, zeroth edition, to be available July 6th, that we update on a continuous basis, as tasks are completed. For sections other than those contributed by Ken, the deadline would be two weeks from today (today is 6/26/98).

Some tasks to be completed, to complete document:

1. Comparison of NS shapes with TOSCA ray trace (with target energy loss - Phil Roos
2. Choice of scintillator length. This interacts with item (3) because of the close packing at the front. - NS/KMcF
3. Choice of configuration (one/two scints, one/two light guides). Use of FPD for backward vs. separate hodos? REMINDER: the current reference configuration is FPD: two scints with 3 mm air space, two guides per scint; CED: single scints with - All? -- need proponents of these configurations
4. Optical simulation of proposed configurations to predict performance. - DavidA
5. One-detector Prototype construction, long counter construction and test. Wm&Mary, UMd, others
6. Decision on amplifier vs. no amplifier. - TRIUMF-Manitoba, KMcF, electronics group
7. Completion of light guide design for candidate configurations - KMcF
8. Completion of support structure design
9. Decision on diagnostic techniques:
   1. two fibers per scint?
   2. moving source?
   3. "probe" counters?

Below is the current outline of the document. It needs some revision. However, tentatively names have been added of responsible individuals to the outline, for the appropriate sections. A question mark means we need to identify a volunteer. We need to revise this outline to include the following parts:

• 1.1.2 TOSCA ray tracing - Phil Roos
• 3.3 Manufacture - GreggF
• Background issues - NS
  1. energy deposit spectrum; energy spectrum of particles depositing energy by type (electron, proton)
  2. Rates, real and background (or hits/beam electron) in forward scattering
  3. Rates in backward scattering
• PMT aging issues - TRIUMF/Manitoba
• Expanded (separate?) section on prototype studies - UMd-Wm&Mary-CMU

1. Detector system overview

1.1. Overall design goals and methods

1.1.1. Goals

Proton and electron detector arrays (FPD, CED)... - NevenS

1.1.2 Methods

Fast parameterized trajectory simulation (finite-thickness target,...), - NevenS
version of Guideit,... - KMcF

1.1.3 Changes since TDR:

• All FPD counters approx. perpendicular to rays FPD Counters doubled to reduce accidental backgrounds
• PVT scintillator (BiCron BC408) selected over acrylic
• FPD Q2 range extended to 1 (Gev/c)²
• FPD Q2 definition
• Q2 defined in region 0.12 to 0.5 (GeV/c)² by detector in conjunction with ToF to reject background.
• Above 0.5 (GeV/c)²
• Q2 is defined primarily by ToF.
• CED addded

2. FPD Detector (scintillator) design

2.1 Criteria

2.1.1 Design approach

Same-rate intervals at low Q2, Q2 by ToF at higher Q2, restricted counter physical width to enhance light collection - NS/KMcF

2.1.2 Acceptance vs. Q2, phi, target z.

Knowledge of mean Q2, knowledge of shape of acceptance for each bin of Q2. - NS/KMcF

2.1.3 Efficiency of system compared with ideal - NS/KMcF

2.1.4 Double counting fraction (particles hitting more than one detector) - NS/KMcF

2.1.5 Collimator scattering - NS/KMcF

2.1.6 Effect of detector misalignments

Acceptance, double hits, uncertainty in Q2 acceptance, asymmetry about center line as source of false asymmetry - NS/KMcF

2.1.7 Effect of magnet misalignments - NS/KMcF

2.1.8 Light collection efficiency - NS/KMcF

2.1.9 Dynamic range (low-energy protons vs. min. ionizing) - NS/KMcF

2.2 Reference design -- FPD

2.2.1 Momentum intervals - NevenS

2.2.2 Physical layout - NS/KMcF

2.2.3 Acceptance and double counting - NevenS

2.2.4 Misalignment sensitivities - KMcF

2.2.5 Material - KMcF

2.2.6 Simulation - DavidA

2.2.7 Manufacture

Water-jet, NC mill, hand-polish - KMcF

2.2.8 Prototype studies - DavidA

light collection, no. of p.e.'s... - PhilRoos

3. FPD light pipe design

3.1 Criteria - KMcF

3.2 Simulation - DavidA

3.4 Prototype studies - Breuer/Cowley/GreggF

4. CED detector design

4.1 Criteria

4.1.1 CED inelastic rejection

4.2 Reference design -- CED

4.2.1 Physical layout -- match to FPD

4.2.2 Acceptance

4.2.3 Misalignment sensitivity

5. CED light pipe design

5.1 Criteria

5.2 Simulation

5.3 Manufacture

5.4 Prototype studies

6. PMT and potential divider - TRIUMF/Manitoba/KMcF

6.1 Criteria

6.2 Selection of PMT for FPD

6.3 Potential divider design

6.4 Case design

6.5 Prototype studies

7. Light-pulser system - Steve Pate NMSU

7.1 Goals

7.2 Design

7.3 Prototype studies

8. Configuration and Support structure

8.1 Overview - KMcF/SL

• General approach is modular design
• Requirements:
  • Cryostat head, shielding, scintillator placement (keep-out zones)
  • Assembly requirements -- FPD, CED
  • Matching to target/magnet
  • Survey issues, misalignment issues
  • Transition from forward to backward scettering layouts

8.2 Mechanical properties of scintillator and light pipe

deflection under own weight, likely forces.

8.3 Support structure overview

global and module

8.4 FPD module

• Overall structure
• Detector mount
• Light pipe mount
• PMT mount
• Light exclusion
• Deflection under load
• Assembly

8.5 CED module - LaTech

• Overall structure
• Detector mount
• Light pipe mount
• PMT mount
• Light exclusion
• Deflection under load
• Assembly

8.6 Assembly - SL/?

• Support frame in Hall
• FPD module assembly to support frame
• CED module assembly to support frame
• Support frame to cryostat

8.7 Alignment - SL/?

8.8 Scenario for move from forward to backward scattering

9. Schedule (affects cost). - RhettWoo

10. Cost

This will include cost estimates, justifications and some approach to contingency. Justification willve some hierarchy, with "already purchased" having the highest rating.

10.1 FPD

• scints, including preparation
• light pipe
• PMT
• Potential divider and case
• (cables, HV ?)
• Support structure
• wrapping
• mounting
• survey
• light exclusion
• light pulser
• Assembly
• QA

10.2 CED

• scints, including preparation
• light pipe
• PMT
• Potential divider and case
• (cables, HV ?)
• Support structure
• wrapping
• mounting
• survey
• light exclusion
• light pulser
• Assembly
• QA

10.3 Module supports

Design, manufacture, QA

10.4 Global framework

Design, manufacture, QA

10.5 Test assembly of modules to frame, survey

10.6 Assembly in Hall

10.7 Overall QA